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Question about wide angle distortion of faces

Discussion in 'Open Discussion' started by dpswbab, May 14, 2016.

  1. dpswbab

    dpswbab Mu-43 Regular

    85
    May 30, 2014
    I am generally aware of most of the differences between full frame and so-called crop sensors. However, I have one question I have not been able to find answered anywhere. If I take a headshot from the same position with a FF camera and 24mm lens and a mu43 camera with a 12mm lens, will the person's face be more distorted with the mu43 system. I tend to think it will be, but I don't have the FF gear to run a comparison. Thanks for any knowledgeable insights.
     
  2. palombasso

    palombasso Mu-43 Regular

    61
    Jan 31, 2014
    distortion comes from perspective, and perspective is influenced only by the distance between camera and subject, so as I see it if your position is the same the distortion is going to be the same.

    if you instead kept the same lens and doubled the distance from the subject to maintain the same framing the m43 would be less distorted.




    Sent from my iPad using Tapatalk
     
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  3. ijm5012

    ijm5012 Mu-43 Hall of Famer

    Oct 2, 2013
    Pittsburgh, PA
    Ian
    It could be because it technically is a wider focal length lens (it is a 12mm lens vs. a 24mm lens, but it just gives a similar FoV because of the sensor crop).
     
  4. wjiang

    wjiang Mu-43 Hall of Famer

    Distortion characteristics are the same for ANY format. As long as you have a flat sensor, and a rectilinear lens, it's pretty much about angle of view: Perspective distortion (photography) - Wikipedia, the free encyclopedia

    As a 24mm on FF gives the same angle of view as 12mm on a exact 2x crop from the same distance, the level of rectilinear distortion is the same.

    More generally though, a 24mm on FF can give the same level of rectilinear distortion as 24mm on an exact 2x crop from the same distance, as long as you keep the angle from the subject to the centre of the imaging axis the same, i.e. putting the subject at about half way across the frame (it's actually some trig function, not half-way) on FF gives the same distortion as putting the subject at the edge of frame on a 2x crop. Same thing happens if you take a 24mm lens and compare to a 12mm lens on the same format.

    As long as you keep distance from subject, and angular distance of subject to centre of axis the same, you can crop down the wider shot to get the same result (as far as distortion is concerned). The subject just looks smaller and there's less view around it due to the crop.
     
    Last edited: May 14, 2016
  5. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    This comes up periodically, though it is most often in the form of bloggers spreading misinformation like "you need a true 85mm focal length for portraits" as a way to dismiss lenses like the PanaLeica 42.5/1.2 or Fuji 56/1.2 as truly high-end lenses for portraiture.

    As mentioned above, the only thing that matters for perspective distortion is the distance to the subject.

    Sometimes people mix up perspective distortion with lens distortion as an optical aberration (with fisheyes being the extreme example of this), and it's true that it can be harder to correct optical aberrations in the form of minor barrel or pincushion distortion on smaller physical focal lengths, but those effects are extremely minor in comparison to perspective distortion.

    The Wikipedia article on the subject is informative: Perspective distortion (photography) - Wikipedia, the free encyclopedia
    And this is one of the better articles I've seen to debunk the oft-spread myth about focal lengths: Perspective - Correcting an Oft-repeated Myth - Admiring Light

    Really, the easiest and most obvious way to understand it is to look at the extremes, and realize that focal length cannot be a determining factor in this conversation.

    This portrait was taken with a 90mm lens:

    It is so cartoonishly distorted that the woman's head is nearly as wide as her hips, and her nose is almost 1/3 the width of her entire face. 90mm, of course, is a classic portrait length on FF cameras, and is a telephoto on Micro Four Thirds. So how is it that the image looks so ridiculous? Well, it happened to be taken on a large format camera, so when you take into account the crop factor, it's basically the same as sticking a 25mm FF wide angle lens right in someone's face.

    Now think of an iPhone, or some other smartphone. Those cameras have crazy 4mm lenses. That would be a circular fisheye on M4/3, and if it were even optically possible would be able to see behind itself on a FF camera. But iPhone photos look totally normal - in fact, they are probably the most "normal" photos that exist today. And that's because that 4mm focal length corresponds to a 30-35mm focal length on a FF camera, so just a standard wide-normal lens.

    Subject distance and angle of view are the only things that matter.
     
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  6. oldracer

    oldracer Mu-43 All-Pro

    Oct 1, 2010
    USA
    I would say it even more simply: Subject distance is the only thing that matters.

    Try this gedanken experiment or do it for real: With the camera a fixed distance from the subject, shoot three photos with three different focal length lenses. Crop all the pictures so that the portrait framing is the same and compare. The perspective is the same for all three. It has to be because the camera didn't move.

    The reason that angle of view gets into this is that a wide angle lens tempts us to move closer to the subject to get the framing we want. Then if we don't like the result, we blame the lens for the sin that we ourselves have committed. (That is not to say that there is anything wrong with tight portraits shot with wide angle lenses if that perspective is what you want. They can be a lot of fun*.)

    IMO the reason that the 85-105mm lens range is considered to be "portrait" lenses is that for reasonable framing those lenses put us at a camera distance from the subject that is similar to the distances within which we normally interact with people. So the portrait looks "normal."

    *This one is hardly great art, but it always makes me smile. The little guy in front really wanted a taste of my 9-18mm, set at 9!

    upload_2016-5-15_11-22-55.
     
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  7. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    Yep, exactly. Whenever someone gets on a high-horse about "true" focal lengths, I like to put my 14-140 on a tripod and then crop the 140mm section out of the 14mm image and overlay them in Photoshop. They are, of course, identical. Somehow, even a demonstration as clear as this rarely manages to cut through the cognitive dissonance, unfortunately...
     
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  8. dwig

    dwig Mu-43 Top Veteran

    622
    Jun 26, 2010
    Key West FL
    Of course, this is true if, and only if, you use those lenses on a "miniature" format camera (read: 35mm Full Frame). Real men don't use an 85mm lens for portraits; they use a 12-14" (~300-360mm) lens on their 8x10 view camera. :)

    BTW, criticals points are that the distances that influence perspective are the relative distances to the foreground, subject, and background and that those distances are to be measured from the optical center (front nodal point) of the lens and not from the film/sensor. The "proper" portrait lens for the above mentioned 8x10" camera is shorter relative to the film size than the lens that would produce the same working FOV (at working distance, not the manufacturer's "at infinity" spec). This is because a normal head & shoulders shot on an 8x10" camera is done at approx 1/2 lifesize with substantial bellows extension. It is not the FL relative to the image size that determine FOV. It is, instead, the FL + extension from infinity that matters. With many "antique" lens designs you extend the lens to focus closer. With "modern" lenses (internal focus and most modern varifocals), and "antique" front-element focusing lenses, focusing is often accomplished by changing the FL.
     
  9. oldracer

    oldracer Mu-43 All-Pro

    Oct 1, 2010
    USA
    Of course. I guess I missed the fact that the OP was interested in 8x10" cameras.

    Your use of the word "miniature" is quite quaint. A breath from the 1920's and 1930's when Barnack and Leitz introduced the Leica, an amazing device designed to make miniature images on movie film. I doubt that most M43-ers would think to call 35mm FF "miniature."


    That's esoteric enough that I'm not going to plow through it. You're probably right but my thing is taking pictures, not worrying about nodal points and lens extensions.
     
  10. dpswbab

    dpswbab Mu-43 Regular

    85
    May 30, 2014
    Thanks for all the info, everyone. You've given me the handle on this subject I was looking for.
     
  11. phigmov

    phigmov Mu-43 Hall of Famer

    Apr 4, 2010
  12. palombasso

    palombasso Mu-43 Regular

    61
    Jan 31, 2014
    I´ve read the Lensrental post and while very visual it still mentioned focal length as affecting background compression, which is not true.
    Background compression is only about camera x subject x background distances.

    I did a little in-house test with the Panasonic 45-175 shot at 50, 100 and 150 at 3 different distances from the subject and cropping the shorter focal lenght pictures to match the longer ones.
    cropped.

    The 50mm cropped to the 150mm field of view gives the same final perspective and background compression (but more depth of field).

    Longer focal lenghts may still be more desirable for portraits for giving slimmer depth of field, so more background blur, at the same f-stop, not mentioned all the pixels wasted by cropping so much.
     
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  13. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    I think you used the wrong word, 'distorted'.

    What you IMHO were searching for was the term 'unnatural perspective'. Although this is sometimes called perspective distortion, so I sympathise.

    And, as has been amply explained by prior comments in this thread, the only thing that matters is how far the camera is from the subject.

    P.S. as an unhelpful aside, the only truly objectively natural perspective is when the subject is an infinite distance from the camera. Only then will foreground and background objects appear at their correct relative size. However, a subjectively natural perspective occurs when the camera is a similar distance from the 'view' as a human observer would stand.
     
  14. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    Quote of the day from Kirk Tuck's blog today, relates to this thread about wide angle photography: "Few people are really good at composing with wide angles but many people absolutely believe that they are the exception.....".
     
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  15. pellicle

    pellicle Mu-43 All-Pro

    Feb 10, 2010
    Southport, OzTrailEYa
    pellicle
    Hi

    agreed ... and well done in going to the effort to illustrate this. The fact is that its mainly about aperture diameter not f number. I wrote a post some years back on my blog to illustrate this

    in my view ...: focal length, angle of view, aperture and DoF

    so similar to yours with different distance scales:

    overview
    4364006855_fd71d37c15.

    then each with the same diameter aperture, not moving the camera, just cropping

    21mm
    4364007083_df45ff6a7b.

    50mm
    4364748656_549f00fd60.
    100mm
    4364006915_8c050c7faf.
     
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  16. Jonathan F/2

    Jonathan F/2 Mu-43 Hall of Famer

    Aug 10, 2011
    Los Angeles, CA
    You should speak for yourself. :rolleyes:
     
  17. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    Kirk Tuck spoke for many.